Cleavage and polyadenylation specificity factor subunit 3

Component of the cleavage and polyadenylation specificity factor (CPSF) complex that play a key role in pre-mRNA 3'-end formation, recognizing the AAUAAA signal sequence and interacting with poly(A) polymerase and other factors to bring about cleavage and poly(A) addition. Has endonuclease activity, and functions as mRNA 3'-end-processing endonuclease. Also involved in the histone 3'-end pre-mRNA processing. U7 snRNP-dependent protein that induces both the 3'-endoribonucleolytic cleavage of histone pre-mRNAs and acts as a 5' to 3' exonuclease for degrading the subsequent downstream cleavage product (DCP) of mature histone mRNAs. Cleavage occurs after the 5'-ACCCA-3' sequence in the histone pre-mRNA leaving a 3'hydroxyl group on the upstream fragment containing the stem loop (SL) and 5' phosphate on the downstream cleavage product (DCP) starting with CU nucleotides. The U7-dependent 5' to 3' exonuclease activity is processive and degrades the DCP RNA substrate even after complete removal of the U7-binding site. Binds to the downstream cleavage product (DCP) of histone pre-mRNAs and the cleaved DCP RNA substrate in a U7 snRNP dependent manner.

COFACTOR:

Binds 2 zinc ions per subunit.

SUBUNIT STRUCTURE:

Component of the cleavage and polyadenylation specificity factor (CPSF) complex, composed of CPSF1, CPSF2, CPSF3, CPSF4 and FIP1L1. Interacts with CPSF2, CSTF2 and SYMPK. Interacts with TUT1; the interaction is direct and mediates the recruitment of the CPSF complex on the 3'UTR of pre-mRNAs. Interacts with WDR33.